PLANAR MAGNETIC DEVICES EXHIBITING ENHANCED THERMAL PERFORMANCE
A magnetic device, such as an inductor or transformer, having enhanced thermal performance characteristics includes first and second parallel adjacent conductive layers patterned to define conductive spiral traces, wherein the traces are geometrically patterned to avoid overlapping of gap areas defined between the adjacent spiral traces, and thereby provide for improved heat transfer between adjacent conductive layers in the device.
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This disclosure relates to planar magnetic components using printed circuit boards (PCB) as the winding carrier, and more particularly to planar magnetic components in which the electrically conductive windings in adjacent layers are configured to enhance thermal performance.
BACKGROUND OF THE DISCLOSUREIn order to achieve better reproducibility, more compact designs, and greater economy, as compared with wire windings, planar magnetic components on PCB are being increasingly and advantageously employed in a variety of applications, especially in transportation (e.g., automotive) and portable electronics (e.g., mobile telephones) applications. These devices comprise spiral conductive traces defined in or on planar layers of a PCB having multiple conductive layers in a stacked arrangement with different conductive layers in the stack appropriately electrically connected with vias to produce a magnetic component, such as a transformer or an inductor. The conductor layers are physically separated by an electrical insulator or dielectric material, typically a glass fiber reinforced epoxy resin, which is typically a very poor thermal conductor. As a consequence, higher power magnetic components can develop hot spots that overheat, and over time can cause premature deterioration and failure of the component.
The conventional solution was to increase the thickness or width of the conductive winding so that high thermal gradients are dissipated by thermal conduction through the electrical conductors. This is a viable and often acceptable solution. However, this solution increases the size and mass of the component, reducing or eliminating some of the benefits of employing planar magnetic components on PCB. Such increase in size and mass is particularly undesirable in portable electronic devices.
Accordingly, there is a need for planar magnetic components on PCB that provide better thermal performance while also minimizing the amount of conductive material needed.
SUMMARY OF THE DISCLOSUREDisclosed is a planar magnetic device, such as an inductor or transformer having first and second parallel adjacent conductive layers separated by a layer of dielectric material, in which each of the conductive layers is patterned to define a spiral conductive trace having more than a single turn or winding to define a gap between windings, wherein the geometric pattern of the traces is selected so that at least a portion of the gap area between turns of the conductive trace in one layer is not aligned with the gap area between turns of the adjacent spiral trace.
A conventional magnetic device 10 is illustrated in
A single electrically conductive layer defining a spiral conductive trace 12 having three turns or windings is shown in
For the conventional magnetic device 10 shown in
In addition to having identical overlapping traces, the conventional device 10 has traces that have a uniform width along the length of the spiral trace. It is believed that designers thought that a uniform width along the length of the spiral trace would provide the lowest electrical resistance.
It has been determined that very substantially improved thermal performance can be achieved by varying the width of the trace along the length of the trace for at least one of two adjacent conductive layers. The improved design is illustrated in
In certain preferred embodiments, first and second parallel adjacent conductive layers separated by a single layer of dielectric material, each define spiral conductive traces having more than a single turn or winding, wherein the geometry of the traces is selected so that any straight line perpendicular to the parallel adjacent conductive layer intersects at least one of the conductive spiral traces (i.e., all gaps in the adjacent traces are not aligned). The number of turns is typically, but need not be, an integer. For example, the number of turns could be 1.5, 2.25, 2.5, or any other value greater than 1. The arrangement in which no gaps are aligned provides excellent thermal characteristics, with the outer most turn in the conductive spiral traces being only a few degrees (e.g., 5° C., 10° C. or 20° C.) higher than the inner most turn. However, improvements in accordance with the principles disclosed herein can be achieved even when less than all gaps in the adjacent traces are not aligned. In this regard, the disclosed magnetic devices encompass those having two adjacent spiral traces with more than a single winding in which at least 5%, 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80% or 90% of the gap area (total area between turns of the conductive trace) is not aligned with the gap area of the adjacent spiral trace.
The illustrated embodiments are exemplary only, it being understood that any number of conductive layer pairs can be used and that the width of at least one layer of each conductive layer pair has a width that varies along its length.
The above description is intended to be illustrative, not restrictive. The scope of the invention should be determined with reference to the appended claims along with the full scope of equivalents. It is anticipated and intended that future developments will occur in the art, and that the disclosed devices, kits and methods will be incorporated into such future embodiments. Thus, the invention is capable of modification and variation and is limited only by the following claims.
Claims
1. A planar magnetic device, comprising:
- first and second parallel adjacent conductive layers separated by a layer of dielectric material, each conductive layer patterned to define a spiral conductive trace having more than a single turn or winding to define a gap between turns, the geometric patterns of the spiral conductive traces each defining a gap area between turns, wherein at least a portion of the gap area defined by a first of the spiral traces is not aligned with the gap area defined by the adjacent spiral trace.
2. The planar magnetic device of claim 1, wherein at least one of the spiral conductive traces has a width that varies along its length.
3. The planar magnetic device of claim 1, wherein at least one of the spiral conductive traces has a width that varies continuously from the inner most turn to the outer most turn.
4. A planar magnetic device, comprising:
- a PCB having a first electrically conductive layer defining a first spiral conductive trace, a second electrically conductive layer defining a second spiral conductive trace, and a single dielectric layer disposed between the first and second electrically conductive layers, a width of the first conductive trace changing along a length of the first conductive trace so that all gaps between adjacent turns in the second conductive trace are overlapped by the first conductive trace.
Type: Application
Filed: Jul 21, 2019
Publication Date: Jan 21, 2021
Applicant: Kostal of America, Inc. (Troy, MI)
Inventors: Alan Joseph (Shelby Township, MI), Joel Anderson (Ferndale, MI)
Application Number: 16/517,612